Antinuclear antibodies (ANAs) are present in more than 30% of patients with hepatocellular carcinoma (HCC) but little is known of the significance of this observation or the identity of the nuclear autoantigens. The aims of this research proposal are to characterize the molecular structure and biological function of the nuclear and nucleolar antigens which are targets of autoantibodies in HCC and to initiate a prospective study to determine the relevance of changing ANA titers and specificities, a phenomenon which was observed in some patients with liver cirrhosis and chronic hepatitis who developed HCC. This is a collaborative effort with investigators at Shinshu University Hospital in Matsumoto, Japan who have a large collection of sera from patients with HCC and who are following a large cohort of patients with chronic liver disease associated with viral hepatitis. Initial studies have already shown that three nucleolar antigens associated with HCC are RNA processing and a nucleolar protein associated with cellular commitment to DNA synthesis and cell proliferation. The hypothesis to be examined is that ANAs are immune responses to intracellular proteins involved in growth and proliferative processes associated with carcinogenesis and that ANAs could be used as probes to identify these proteins and their cognate functions. Autoantibodies will be used to probe cDNA expression libraries and isolated cDNA clones will be analyzed to characterize encoded proteins. The dynamic nature of ANA responses in HCC will be investigated in a prospective study of patients with viral hepatitis-related liver cirrhosis and chronic hepatitis in Japan. It is known that some of these patients will develop HCC and sera will be obtained at regular intervals and examined for conversion from ANA-negative to ANA-positive status, for increases in ANA titers and for changes in ANA specificities. Patients showing these changes will have extensive diagnostic procedures to determine if the autoantibody alterations are reporters of early carcinogenesis. If certain regulatory pathways associated with cell growth are perturbed in carcinogenesis, identification of components of these pathways might be achieved by using autoantibodies.